Remotely controlled multifunction spotlights and a control system for such lights is described in U.S. Pat. No. 4,392,187, by which the colour and position of the beam from each of a number of spotlights in a system, can be controlled from a single control console. In common with other lighting control systems such as that described in earlier U.S. Pat. No. 4,095,139, the system in 4,392,187 uses a single transmission path between the control console and the spotlights in the system, and serial data streams, each having a precursor which is only recognised by one of a plurality of data receivers associated with the spotlights, so that serial data for controlling the different spotlights can be routed automatically to the appropriate spotlight, via its associated receiver, without causing any response in the other spotlights.
Such systems have the advantage that only a single conductor pair is needed around the entire system to convey the digital control signals to the various control devices within the different spotlights. There is thus a considerable saving in the amount of cabling required to set up and interconnect the lights--but the spotlights concerned are not suitable for control by analogue control signals such as may be obtained from a mixing desk or console, a number of potentiometers, usually in the form of linear potentiometers, each having a sliding control for adjusting the output voltage/current from a minimum to a maximum value, as required.
In an analogue system, if six functions are to be controlled in each light, the control signals from six potentiometers will need to be supplied to each light by way of for example a six core cable with a common return path which may double up as one of the conductive paths providing operating current for the lamp.
There are many existing installations which can produce analogue signals as a large number of separate channels. Complete with control console and wiring. However it is often desirable to be able to update or replace some of the spots, to enable special effects to be produced or to extend such systems by the addition of new spotlights, and it is one object of the present invention to provide an improved multifunction spotlight which can be controlled from either a multichannel analogue control system or a single wire serial data digital control system. In this way new spotlights can be added to an exisiting system in the full knowledge that if and when the multichannel console is replaced by a digital console, these new spotlights can still be employed in the new system.
It is a further object of the invention to provide an improved multifunction spotlight for use with either type of control system, by which N facilities can be controlled using only n channels of control signals (N being greater than n)--either analogue or digital.
It is a still further object of the invention to provide an improved multifunction spotlight having controllable parameters such as beam position and colour, which can be controlled from a conventional multi-channel lighting control console of the type previously only designed to provide one analogue control signal to an appropriate fader to vary the light intensity of each of a plurality of spotlights.
It is a further object to provide a control system for the currents to a bipolar stepper motor to enable the transistions between stable postions of the armature to be achieved smoothly.